Refrigerating apparatus of dissimilar metals



Nov. 6, 1956 1.. H. GRFNELL 2,759,318

REFRIGERATING APPARATUS OF DiSSIMILAR METALS Filed Aug. 19, 1952 INVENTOR. Leland H. Grenell,

BY MZ 1 $4 ATTORNEYS United States Patent O l REFRIGERATING APPARATUS F DISSIMILAR METALS Leland H. Grenell, Oakwood, Ohio, assiguor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application August 19, 1952, Serial No. 305,219

4 Claims. (Cl. 62-115) This invention relates to refrigerating apparatus and more particularly to a system in which some portions of the refrigerant circuit are made of steel and other portions are made of aluminum and wherein one or more special welded joints are provided between the aluminum and the steel portions.

The desirability of utilizing aluminum evaporators and tubing has long been recognized but the use of aluminum evaporators presents a problem when it comes to connecting it in circuit with the compressor which is made of steel. It is recognized that it is possible to weld aluminum to steel with the use of a flux but portions of the flux will be deposited on the interior surfaces of the tubing or parts being welded and this flux within the system constitutes a problem.

It is an object of this invention to provide an arrangement which eliminates the need for using a flux in joining the aluminum to the steel.

The temperature required for making a good welded joint between aluminum and steel presents another problem in that the aluminum at the joint tends to soften and become distorted during the welding operation and is left weakened. This weakening of the joint is objectionable, especially in a refrigerating system where the compressor vibrates and is joined to non-vibrating elements.

It is an object of this invention to provide an improved type of joint between an aluminum refrigeration line and a steel compressor which is capable of withstanding the vibrational stresses encountered.

Another object of this invention is to provide a welded joint between an aluminum refrigerant line and a steel refrigerant line wherein the steel projects into the aluminum line far enough to reinforce the aluminum line at the point where the aluminum might have been weakened by the welding operation.

Still another object of this invention is to provide an improved joint which eliminates the tendency for restriction in the internal passage due to the welding operation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.

In the drawing:

Figure 1 is an elevational view, largely schematic, showing a refrigerating system constructed in accordance with my invention; and

Figure 2 is a fragmentary elevational view with parts broken away showing one of the welded joints.

Referring now to the drawing, wherein there is shown a preferred embodiment of the invention, reference numeral designates a conventional sealed motor-compressor unit of the type having a steel external housing through which the inlet and outlet lines 12 and 14 respectively project. By using steel inlet and outlet lines, they may be silver soldered to the compressor housing in accordance with standard practice. The outlet line 14 is connected to an aluminum condenser 16 by means of a 2,769,318 Patented Nov. 6,

welded joint 28 Which will be described more fully hereinafter. The condensed refrigerant drains into a receiver 16 from whence it flows to a plate type aluminum evaporator 20 through an aluminum restrictor 22. The refrigerant vaporized in the evaporated 20 feeds into an aluminum return line 24 which is connected to the steel tube section 12 by means of a welded joint 26 of the type illustrated in Figure 2 of the drawing.

In order to eliminate the need for using flux in making the joints 26 and 28, the projecting ends of the inlet and outlet steel tube sections 12 and 14 are precoated with aluminum as indicated at 30 so as to make it possible. to inert gas weld the aluminum tubing to the aluminum coating on the steel tubing. Any one of several well-known processes of coating the steel tubing with aluminum may be used. In coating the ends of the steel tubes, a flux can be used, if desired, since the ends of the tube can be pinched closed during the precoating process so as to prevent the introduction of any of the flux into the interior of the tube. After this initial coating has been added, the pinched ends of the tube can be cut off.

The steel tube sections 12 and 14 are in effect adapters each having one portion coated with aluminum for attachment to aluminum elements and each having another uncoated steel portion for attachment to the steel compressor. A silver soldered joint can then be formed between the uncoated portion and the compressor.

Being the joints 26 and 28 are similar, only the one will be described. In attaching the aluminum refrigerant line 24 to the aluminum coated steel tube section 12, the end of the aluminum tube is expanded suficiently so as to overlap the steel tube throughout a predetermined distance as shown in Figure 2. This distance is enough so that that portion of the aluminum tubing which may be weakened by the welding operation is reinforced by the steel tube section 12. After the aluminum tube has been overlapped with the aluminum coated steel tube, the end of the aluminum tube is are Welded to the aluminum coating 30 as indicated at 34. This welding is done without the use of any flux after the aluminum has been thoroughly cleaned. The welding is preferably done in an atmosphere of inert gas so as to prevent oxidation of the aluminum at the weld. By virtue of the above described method and construction, it is obvious that a gas tight joint may be provided and that any weakening of the aluminum tube 32 adjacent the weld 34 is of no consequence as the projecting end of the steel tube 12, reinforces the aluminum tube at the point where it may have been weakened.

For purposes of illustration, the aluminum to steel joints have been shown adjacent the compressor whereas these joints could be located elsewhere in so far as certain aspects of the invention may be concerned. Thus, for purposes of illustration there has been shown a system wherein both the evaporator and condenser are made of aluminum whereas one or the other of these may be made of some other material such as stainless steel or brass, but wherever a joint is formed between a steel tube and an aluminum tube the joint would be made as shown in Figure 2.

The joint between the aluminum portion and the steel portion is preferably made by inserting a section of aluminum coated steel tubing into a section of aluminum tubing Whereas the joint could also be made by inserting the aluminum coated steel tubing directly into the inlet of an aluminum evaporator or condenser. Thus, in connecting a steel section of tubing to a plate type aluminum evaporator one would coat with aluminum the one end of the steel tubing and insert the same directly into the inlet of the evaporator and then weld the aluminum evaporator to the aluminum coating.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In a refrigerating system, a motorcompressor unit having steel inlet and outlet lines connected thereto, a condenser element, an evaporator element, means for connecting said motor-compressor unit, condenser element, and evaporator element in refrigerant flow relationship, at least one of said elements being made of aluminum and connected to one of said steel lines by means of an aluminum tube having its one end arranged in overlapping relationship to said one steel line, said steel tube having an aluminum coating provided thereon at the point where it projects into said aluminum tube, and a weld between said aluminum tube and said alumi num coating.

2. In a refrigerating system, a compressor unit having steel inlet and outlet lines connected thereto, refrigerant condensing and evaporating means joined to said inlet and outlet lines, at least a portion of said means including an aluminum element, means for joining said aluminum element to one of said steel lines comprising an aluminum coating provided on said one steel line and a weld between said aluminum element and said coating 3. In a refrigerating system, a motor-compressor unit having steel inlet and outlet lines connected thereto, a

condenser element, an evaporator element, means for connecting said motor-compressor unit, condenser element, and evaporator element in refrigerant flow relationship, said last named means comprising aluminum tubing having a portion arranged in overlapping relationship with one end of one of said steel lines, said one steel line having an aluminum coating provided on its said end, and a weld between said aluminum tubing and said aluminum coating.

4. In a refrigeration system, a steel compressor, an aluminum evaporator, fluid flow means connecting said compressor to said evaporator including aluminum tubing and a steel tube section having one portion coated with aluminum, a silver soldered joint between said compressor and the uncoated portion of the steel tube section, and an inert gas weld between said aluminum coating and said aluminum tubing, said steel tube section projecting into said aluminum tubing to a point beyond said inert gas weld.

References Cited in the file of this patent UNITED STATES PATENTS 1,776,615 Boothman et al. Sept. 23, 1930 2,102,325 Kylstra Dec. 14, 1937 2,309,797 Stickel Feb. 2, 1943 2,386,889 Furry Oct. 16, 1945 2,481,614 Redmond Sept. 13, 1949 2,513,365 Rogoff July 4, 1950 

